<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
      
     
  @keyframes myframes{
            0%{
                width: 200px;
                height: 200px;
                background-color: purple;

            }
            50%{
                width: 800px;
                height: 400px;
                background-color: yellow;
            }
            75%{
                width: 1000px;
                height: 600px;
                background-color: lightblue;
            }

            100%{
                width: 200px;
                height: 200px;
                background-color: blue;
            }


        }
        div{
            width: 200px;
            height: 200px;
            background-color: red;
            animation-name: myframes;
            animation-duration:1s;/*播放时间*/
            animation-timing-function: ease-in;
            animation-delay: 1s;/*延迟播放时间*/
            animation-iteration-count: infinite;/* 播放次数*/
            animation-direction: reverse;/*反方向播放*/
            animation-direction:alternate;/*单数正方向播放，偶数反方向播放*/
            animation-direction:alternate-reverse;/*偶数正方向播放，单数反方向播放*/
            
            animation-play-state: running;/*播放*/
            /* animation-play-state:paused; 停止 */
        }




    </style>
</head>
<body>
    <div></div>
    
</body>
</html>